Mohammad Wasay
The Aga Khan University, Karachi, Pakistan
Title: Arbovirus infections of nervous system – trends and threats
Biography:
Abstract:
Arthropod-borne viruses (arboviruses) are among the most important international infectious threat to human nervous system. The neurological diseases that may be transmitted to humans in the traditional way by arthropods include meningitis, encephalitis, myelitis, encephalomyelitis, neuritis (including anterior horn cells and dorsal root ganglia), and myositis. Arboviruses are distributed worldwide. However, different species have predilection for different geographical areas. Arboviruses are transmitted among vertebral hosts by blood feeding arthropod vectors including mosquitoes, biting flies, mites, nits and ticks. Some of the well-known encephalitides include West Nile encephalitis (WNE), Dengue fever encephalitis (DFE), St. Louis encephalitis (SLE), Japanese encephalitis (JE), Toscana encephalitis (TOE), Crimean-Congo hemorrhagic fever (CCHF), Chickeungunya virus encephalitis (CHIKV), Eastern equine encephalitis (EEE), and Western equine encephalitis (WEE). The keys to prevention of arboviral encephalitis include reduction of vector prevalence, reduction of amplifying of host susceptibility, avoidance of vector and reduction in human susceptibility through the use of insect repellants or immunization. With the widespread resistance to chemical control of vectors, novel methods like genetic control of vector populations are becoming increasingly important. The case fatality rate can range from <1% for LCE to as high as 70% in EEE. The case fatality rate for JEE and SLE is up to 30%. Neurological sequelae of arboviruses can result in permanent disability in as high as 90% of affected individuals depending on the virulence and type of the virus.
Table 1. Common arboviruses with their geographical distribution and vectors
|
Family |
Virus |
Vector |
Geographical Distribution |
|
Togaviridae |
|
|
|
|
|
Eastern Equine Encepahlitis Virus |
Mosquito (Culiseta, Aedes) |
Eastern and Gulf coasts of USA, Carribean islands, Central America and northeast coast of South America |
|
Western Equine Encephalitis Virus |
Mosquito (Culiseta, Culex) |
Midwest and Western USA, Canada |
|
|
Venezuelan Equine Encephalitis Virus |
Mosquito (Aedes, Culex) |
South and Central America, Southeast and Southwest of USA |
|
|
Chikungunya Virus |
Mosquito (Aedes) |
Africa, India, Southeast Asia |
|
|
Flaviviridae |
|
|
|
|
|
St. Louis Encephalitis Virus |
Mosquito (Culex) |
North America, Central America and South America |
|
Japanese Encephalitis Virus |
Mosquito (Culex) |
Japan, Northeast Asia, Southeast Asia, Central Asia and Indian Subcontinent |
|
|
West Nile virus |
Mosquito (Culex) |
Africa, Mediterranean region, central Asia, India, Europe, North America, Central and South America |
|
|
Dengue Fever Virus |
Mosquito (Aedes) |
Asia, tropical and subtropical regions of the world |
|
|
Murray Valley Encephalitis Virus |
Mosquito (Culex, Aedes) |
Australia, New Zealand, New Guinea |
|
|
Bunyaviridae |
|
|
|
|
|
California Encephalitis Virus |
Mosquito (Aedes) |
Western USA |
|
|
La Crosse Encephalitis Virus |
Mosquito (Aedes) |
Midwest and eastern USA |
|
|
Toscana Encephalitis Virus |
Sand fly (Phlebotomus) |
Europe, North Africa |
|
|
Rift Valley Fever Virus |
Mosquito (Culex, Aedes and others) |
East Africa, South Africa Nile valley, Saudi Arabian peninsula |
|
|
Crimean-Congo Hemorrhagic Fever Virus (Nairovirus) |
Ticks (Hyalloma, Ixodid) |
Africa, Europe, Asia |
|
Reoviridae |
|
|
|
|
|
Colorado Tick Fever Virus |
Ticks (Dermacentor) |
Rocky mountains of USA |